A structural system supporting a precision sensor, such as a telescope, as its payload may be susceptible to vibration disturbances that result in measurement or pointing errors. Vibration disturbances may be attributed to mechanical components or assemblies, such as reaction wheel assemblies, motors, or pumps that are common in structural systems. Structural systems tend not to have significant inherent damping to attenuate vibrations that may degrade system performance.
Active and passive vibration isolators are designed to attenuate the vibration and to isolate the payload from structural dynamics of the base. One example of a passive-mass damping and isolation system is a D-STRUT™ vibration isolator, manufactured by Honeywell, Inc. of Morristown, N.J. The D-STRUT™ vibration isolator is a three-parameter vibration isolation system that mechanically acts like a spring (KA) in parallel with a spring (KB) in series with a damper (CA). D-STRUT™ vibration isolator is disclosed in U.S. Pat. No. 5,332,070 entitled “Three Parameter Viscous Damper and Isolator” to Davis et al.
The D-STRUT™ vibration isolator includes a hollow shaft and a piston that is configured to slidably move through the shaft. The piston includes a flange that extends radially from a midsection thereof. The flange has a top surface that is coupled to a first sealed bellows and a bottom surface that is coupled to a second sealed bellows. Each of the bellows has a chamber that is filled with fluid. Thus, when the piston moves axially through the shaft, fluid flows from one of the bellows chambers to the other.
An example of an active damping and isolation system is the Hybrid D-STRUT™ vibration isolator, manufactured by Honeywell, Inc. of Morristown, N.J. The Hybrid D-STRUT™ includes the passive damping mechanism of the passive D-Strut™ and an active enhancement mechanism. The active enhancement mechanism enhances the force dissipation of the passive damping mechanism and includes an actuator mechanism which has a voice coil actuator system (such as a Lorentz force actuator). The Hybrid D-STRUT™ is disclosed in U.S. Pat. No. 6,003,849 entitled “Hybrid Isolator and Structural Control Actuator Strut” to Davis and Hyde.
Although conventional passive and active vibration isolators, such as the examples described above, are generally useful for damping vibrations in most circumstances, they may be improved. For example, the vibration isolators may not operate as desired when employed in cryogenic (e.g., below −120° C.) environments. In particular, the fluid that fills the chamber of the vibration isolators may increase in viscosity or change phase from liquid to solid when exposed to such temperatures. As a result, the vibration isolator may not perform as desired. Gases may be used in place of the fluid; however, the gas is typically contained in a highly pressurized chamber, which if damaged, may leak in a vacuum environment.
Accordingly, it is desirable to have a vibration isolator that is improved over conventional vibration isolators. Additionally, it is desirable to have a vibration isolator that may be used to isolate vibration when exposed to cryogenic environment. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.